COLUMBIA  LIBRARIES  OFFSITE 

HEALTH  SCIENCES  STANDARD 

{l||l|ll|lll  III  "■■  ■■ 


s 


t^!JL. 


RECAP 


ISt 


HX641 00650 
QP135  .C81  Thermics  and  thermo- 


THERMICS 


AND 


BY 


F.  J.    B.   CORDEIRO,    M.  D.. 


r.  A.  Surgeon,  U.S.  Navy 


from   The   Sanitarian  /or  Jjily,   i8gy. 


Thermo-Dynamics  of  the  Body,  f 


♦ 
♦ 

y 
y 
? 
? 

T 

t 
5* 


COLUMBIA  UNIVFRSITV      **♦ 

DEPARTMENT  OF  PHYSlOLOfV 

College  of  PHYStctANS  and  Suroeo^' 

4ar  WEST  FIFTY  NINTH  STREET     ♦!« 
NEW  YORK  >! 


BROOKLYN,  N.  Y. 


c«:«:»<K*<t»<«<K*<K»*x*<»<»»x»»x»<«<«H«<»«><KK*<":^^^^^ 


Q<f^'^^ 


CSV 


Columbia  MnitJer^ftp 

intl)e€itpoflfttitork 

College  of  ^ftpgiciansf  anb  ^urgeonsf 
Hibrarp 


THERMICS 


AND 


Thermo-Dynamics  of  the  Body. 


F.  J.   B.   CORDEIRO,    M.  D. 

P.  A.  Surgeon,  U.S.  Navy. 


From    The    SANITARIAN  for   July,    i8gj. 


BKOOKLYN,  N.  Y. 


<^' 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/thermicsthermody01cord 


TFIERMICS 


AND 


THERMO-DYNAMICS    OF    THE    BODY 


By  F.  J.  B.  CoRDEiRO,  M.  D.,  P.  A.  Surgeon,  U.  S.  Navy. 


The  animal  kingdom,  in  regard  to  heat,  can  be  divided  broadly 
into  two  classes — cold-blooded  animals  and  warm-blooded  ani- 
mals. The  former  conform  to  the  temperature  of  their  suround- 
ings,  their  vital-chemical  reactions  taking  place  with  nearly  equal 
facility  through  a  wide  range  of  temperatures.  The  latter  pos- 
sess a  certain  definite  temperature  which  they  maintain  at  all  time? 
and  which  may  be  considered  a  life  function  of  the  species.  The 
difference  is  entirely  one  of  equlibrium. 

All  bodies,  whether  living  or  dead,  must  lose  or  gain  heat  from 
the  surrounding  medium  according  as  their  temperatures  are 
higher  or  lower  than  that  of  the  medium.  In  cold-blooded  ani- 
mals this  loss  of  heat  is  greater  than  the  production,  and  conse- 
quently an  equilibrium  is  not  reached  until  the  temperature  of  the 
body  has  nearly  coincided  with  that  of  its  envelope.  In  warm- 
blooded animals,  on  the  other  hand,  since  life  can  exist  only  within 
certain  narrow  limits  of  temperature,  the  expenditure  and  gain  of 
heat  must  at  all  times  be  nicely  balanced.  Under  different  condi- 
tions it  will  be  seen  that  the  members  of  such  an  equation  may  vary 
widely,  though  the  equality  must  always  be  maintained.  The  body, 
then,  can  be  considered  a  thermostat  set  to  a  certain  vital  tempera- 
ture. 

In  studying  the  movement  of  heat  in  a  body  it  is  essential  to 
know  tliC  specific  heat,  the  penetrability  and  permeability  to  heat, 
of  its  various  parts.  Such  constants  have  unfortunately  (so  far  as 
the  writer  knows),  not  been  determined  for  living  bodies  or  for 
most  animal  tissues.  The  total  quantity  of  heat  in  an  idividual 
would  be  the  sum  of  the  specific  heats  of  its  parts  multiplied  by 
their  masses,  into  the  absolute  temperature,  which  we  may  con- 
sider as  310.     The  average  specific  heat  of  the  body  might  be  de- 


4  T/iermic!<  and   Tlicrriuj-DiiiKuincs  af  titc  BoOij. 

termined  by  observing  the  quantity  of  heat  given  out  by  a  dead 
body  in  cooling  between  two  fixed  temperatures.* 

The  writer,  for  his  own  satisfaction,  has  made  certain  observa- 
tions regarding  the  thermal  constants  of  animal  tissues,  but  since 
proper  facilities  were  lacking,  they  can  be  considered  scarcely 
more  than  surmises.  In  dealing  with  the  problems  shortly  to  be 
taken  up  it  will  be  necessary  to  have  some  idea  in  regard  to  these 
constants,  and  the  following  determinations  will  serve  to  fix  our 
ideas.  According  to  certain  measurements  the  specific  heat  of  the 
blood  is  somewhat  less  than  that  of  water,  though  considerable. 
Its  conductivity  may  be  considered  as  sensibly  equal  to  that  of 
water.  This  is  as  we  should  expect,  since  it  is  composed  so  largely 
of  water  (90  per  cent.),  and  the  direct  consequence  is  that,  owing 
to  its  unceasing  circulation  the  body  has  a  very  high  permeability 
(interior  conductivity).  Whatever  heat  or  cold  is  received 
externally  or  internally  is  quickly  diffused  throughout  the  body 
and  the  internal  equilibrium  is  nearly  maintained  at  all  times.  Not 
that  the  temperature  of  the  body  is  everywhere  exactly  equal,  for 
such  is  not  the  case.  The  exterior  is  hotter  or  colder  to  a  slight 
extent  than  the  interior,  according  as  the  surrounding  medium  is 
above  or  below  the  vital  temperature.  Certain  parts  also,  during 
activity,  may  be  warmer  (muscles,  glands),  and  as  we  shall  see 
later,  cooler  (lungs),  than  the  neighboring  parts,  but  in  general 
the  average  temperature  is  preserved  nearly  uniform. 

We  see  then  that  the  blood,  owing  to  its  high  specific  heat,  con- 
ductivity and  rapid  circulation,  is  eminently  fitted  for  receiving 
large  quantities  of  heat  (or  cold),  and  distributing  it.  It  thus  per- 
forms the  function  of  maintaining  the  internal  equilibrium. 

According  to  certain  rough  determinations  the  specific  heat  of 
the  proteids  is  relatively  small,  that  of  muscle  being  perhaps  .08  of 
water,  while  that  of  the  bones  is  less.  Of  the  solid  tissues  fat 
stands  alone  as  possessing  a  very  high  specific  heat,  perhaps  equal 
to  that  of  blood,  while  its  conductivity  is  small.  We  may  thus 
make  an  estimate  of  the  thermal  capacity  of  the  body  as  possibly 
one-third  that  of  water,  though  in  the  absence  of  exact  determina- 
tions this  can  be  considered  as  scarcely  more  than  a  guess.  As 
fat  is  mainly  situated  directly  under  the  skin,  it  would  seem,  from 
the  foregoing  properties  of  storing  large  quantities  of  heat  and 
parting  with  it  slowly,  to  be  eminently  adapted  to  keeping  the  sur- 

*0n  the  plausible  supposition  that  there  is  no  inarked  difference  between  the  specific  heats- 
of  living  and  dead  tissues. 


TltefDitcs  and   Thermn-Diinamic^  of  the   Body.  5 

face  warm  and  preventing  rapid  losses  at  the  exterior.  However, 
rapid  losses  may  take  place  at  the  suface  under  the  following  cir- 
cumstances. The  skin,  which  in  itself  may  be  supposed  to  have  a 
very  small  penetraiMlity,  is  extremely  vascular,  and  w'hen  a  large 
volume  of  blood  is  flowing,  we  may  say,  in  contact  with  the  sur- 
face, it  may  give  out  or  absorb  a  considerable  amount  of  heat 
according  as  this  surface  is  hotter  or  colder  than  the  surrounding 
medium.  The  coefficient  of  penetrability  of  the  surface  may  there- 
fore vary  from  a  very  small  to  a  very  large  quantity.  It  has  been 
observed*  that,  on  exposure  to  a  low  temperature,  the  naked  body 
loses  heat  from  the  surface  at  first  rapidly,  but  that  soon  the  peri- 
pheral circulation  ceases  almost  entirely;  the  skin  becomes 
blanched  and,  paradoxical  as  it  may  seem,  the  bodily  temperature 
rises  above  the  normal.  In  this  case  it  is  plausible  to  suppose  that 
the  considerable  reduction  of  the  expenditure  of  heat  caused  by 
the  cessation  of  the  surface  circulation  causes  a  temporar}'  storing 
up  of  heat.  It  will  be  seen  subsequently  that  under  the  circum- 
stances there  is  an  increased  production  of  heat,  due  to  com- 
pression of  air  in  the  lungs,  so  that  the  increase  of  temperature  is 
readily  acounted  for.  The  writer  has  also  found  that  by  immers- 
ing the  body  in  hot  water  (41°)  there  was  at  first  a  rapid  absorp- 
tion of  heat  by  the  bodyl  (200  caJories  per  second), but  that  shortly 
the  surface  became  blanched,  showing  a  cessation  of  the  peripheral 
circulation,  and  that  under  similar  conditions  of  temperature,  the 
amount  entering  the  body  from  the  water  (due  allowance  being 
made  at  all  times  for  the  loss  to  the  air),  became  too  small  to  be 
measured. 

The  exterior  of  the  body  is  then,  composed  of  a  cushion  of  fat, 
itself  non-vascular  and  pierced  by  a  few  large  blood  vessels  which 
ramify  extensively  directly  in  contact  with  the  surface. ^ — This  cush- 
ion of  fat  has  a  high  specific  heat  and  low  conductivity.  The  skin 
itself  has  an  extremely  low  conductivity  (no  direct  measurements 
have  been  made),  but  when  filled  with  a  rapidly  flowing  blood  cur- 
rent is  capable  of  emitting  and  absorbing  a  considerable  amount 
of  heat.  Such  an  apparatus  is  an  ideal  one  for  the  admission  or 
exclusion  of  heat  according  to  circumstances.  It  is  extremely  de- 
sirable that  a  series  of  accurate  calorimetrical  experiments  should 
be  undertaken  for  the  determination  of  the  coefificient  of  penetra- 
bility of  the  skin  under  dififerent  circumstances.     We  shall  see 

*  Foster.     Text  Book  of  Phj-siolo^. 

t  Shown  by  the  cooling  of  the  water,  not  by  increase  of  temperature  of  the  bodj'. 


6  Thermlcs  and   Thermo-Dijnamlcs  of  tin-  Boihj. 

later  on  when  we  consider  experiments  on  an  individual  exposed  to 
high  temperatures,  that  this  coefficient  may  become  very  small. 

We  shall  now  attempt  to  write  our  physiological  equation  in  the 
language  of  mathematics  and  afterwards  to  translate  it.  We  have 
seen  that  for  a  warm-blooded  animal  the  sum  of  the  heats  ex- 
pended must  equal  the  sum  of  the  heats  produced,  for  that  is  the 
condition  of  life.  We  shall  endeavor  first  to  tabulate  the  sources 
of  heat  in  the  body  and  measure  these  amounts  as  far  as  is  possible. 
In  its  fullest  expression  such  a  problem  must  be  enormously  com- 
plex, but  in  general  terms  we  may  arrive  at  an  approximate  solu- 
tion. 

Ultimately  all  the  heat  produced  in  the  body  is  derived  from  the 
potential  energy  of  the  food  ingested.  We  can  easily  measure 
the  total  energy  of  a  certain  amount  of  food,  but  this  energy  is 
used  by  the  body  in  such  varying  proportions  and  at  such  varying 
rates  that  little  benefit  would  accrue  to  our  present  problem  from 
such  an  investigation. 

An  important  source  of  heat  in  the  body  is  due  to  the  friction  of 
the  blood  as  it  circulates  in  its  vessels.  All  of  this  resistance,  which 
is  overcome  by  the  heart,  is  transformed  directly  into  heat.  We 
may  calculate  the  amount  approximately.  If  we  suppose  that 
180  CCS.  of  blood  are  expelled  from  the  left  ventricle  at  each  stroke, 
under  a  pressure  of  one-third  of  an  atmosphere,  this  would  corres- 
pond to  .6192  kilogramme-metres  at  each  stroke,  and  at  ^2  strokes 
a  minute,  this  would  give  44.3124  kilogramme-metres  per  minute. 
If  we  suppose  that  the  right  heart  does  one-cjuarter  the  work  of 
the  left,  or  about  10  kilogramme-metres  per  minute,  we  have  for  the 
total  work  per  minute  54.312  kilogramme-metres,  which  corres- 
ponds to  128  calories  per  minute. 

This  is  perhaps  a  rather  high  estimate  for  ordinary  conditions, 
but  where,  as  we  shall  see  later  on,  the  heart  is  forced  to  pump  a 
much  larger  cjuantity  of  blood  in  order  to  maintain  the  normal  tem- 
perature, this  estimate  is  probably  much  exceeded  at  times.  Since 
this  friction  takes  place  largely  in  the  most  constricted  portions  of 
the  circulation,  it  would  be  natural  to  expect  that  the  blood  which 
had  been  driven  through  the  capillary  system  of  a  gland  would 
issue  much  warmer  than  it  entered  and  such  we  find  to  be  the  case. 
Thus  the  blood  of  the  hepatic  vein  has  been  pbserved  to  be  40.73 
while  that  in  the  right  heart  was  37.7.  In  the  muscles  no  con- 
traction can  take  place  without  an  increased  flow  of  blood  through 
them  with  a  simultaneous  constriction  of  the  capillaries,  which 


Uiermics  and  Thermo-Dynamics  of  the  Body.  7 

would  naturally  give  rise  to  a  considerable  production  of  heat — a 
fact  constantly  observed. 

In  the  salivary  glands  during  active  secretion  the  saliva  may  be 
1°  to  1.5°  higher  than  the  blood  in  the  carotid  artery.  In  most 
text  books  of  physiology  this  production  of  heat  is  explained  as  due 
solely  to  glandular  activity  (whatever  that  is),  but  in  view  of  the 
preceding  discussion  we  see  that  a  large  proportion  of  it,  if  not  all, 
must  be  due  to  the  friction  of  the  blood  in  the  gland  capillaries.  If 
a  gland  during  its  action  performs  an  anabolism,  that  is,  elaborates 
a  product  of  a  higher  potential  than  the  material  worked  upon, 
there  must  be  an  absorption  of  heat  equal  to  the  potential  gained. 

On  the  other  hand  where  a  gland  secretes  katabolically  there 
must  be  a  generation  of  heat  equal  to  the  drop  in  potential.  Con- 
sidering the  muscles  as  force  glands,  which  in  fact  they  are.  there 
is  here  undoubtedly  katabolism  which  may  be  wholly  transformed 
into  work,  and  which  would  be  the  case  if  a  muscle  were  an  engine 
of  perfect  efficiency.  Anabolism  also  takes  place  in  a  muscle,  in 
the  heart  probably  during  the  return  stroke,  which  would  be  ac- 
companied by  an  absorption  of  heat. 

Determinations  of  the  efficiency  of  muscles,  with  proper  regard 
for  the  heat  derived  from  the  friction  of  the  blood,  have  not  yet 
been  made.  It  is  probable  that  a  much  higher  elificiency  obtains 
than  is  supposed,  especially  in  certain  automatic  muscles,  such  as 
the  heart  and  respiratory  muscles  which  work  continually  at  a 
constant  rhythm. 

The  heat  due  to  mental  activity  will  not  be  considered,  as  it  is 
extremely  doubtful  if  such  exists. 

To  recapitulate,  then,  we  may  tabulate  as  constant  and  varying 
sources  of  heat  in  the  tody : 

1st.  The  katabolism  of  the  food. 

2d.  The  friction  due  to  the  circulation,  which,  though  varying, 
may  be  considered  to  average  about  180  kilogramme-degrees  in 
the  24  hours. 

3d.  The  heat  absorbed  through  the  surface  when  the  surround- 
ing medium  is  of  a  higher  temperature  than  the  body. 

4th.  The  heat  due  to  ingesta  when  these  are  of  a  higher  tem- 
perature than  the  body.     This  includes  the  inspired  air. 

5th.  Heat  due  to  compression  of  air  in  the  lungs. 

6th.  Whenever  in  external  or  internal  contact  with  the  body, 
any  substance  passes  from  a  gaseous  to  a  liquid  state  (condensa- 
tion), or  from  a  liquid  to  solid  state  (solidification). 


8  Tltermu-x  aii<^   Thcrntn  J)iiiia)n'n:-<  of  the  Bodij. 

It  will  be  noticed  that  glandular  activity  is  not  included  in  the 
above  list,  since  the  heat  generated  in  a  gland  is  probably  either 
frictional  or  katabolic. 

Next,  inquiring  into  the  various  means  by  which  heat  is  lost  to 
the  body,  we  have : 

Tst.  The  loss  through  the  surface  when  the  external  tempera- 
ture is  lower  than  that  of  the  body. 

2d.  Whenever,  in  external  or  internal  contact  with  the  body,  any 
substance  passes  from  a  solid  to  a  liquid,  or  from  a  liquid  to  a 
gaseous  state.  Thus  solution  of  salt  or  sugar  in  any  liquid  is  ac- 
companied by  a  definite  absorption  of  heat.  When  food  is  dis- 
solved by  the  digestive  liquids,  heat  is  absorbed  and  the  resulting 
temperature  is  that  due  to  the  liquefaction  plus,  of  course,  the  po- 
tential energy  lost  when  katobolism  takes  place.  The  evapora- 
tion of  water,  whether  on  the  surface  or  in  the  lungs,  is  of  course 
attended  with  an  absorption  of  heat  which  is  equal  to  the  latent 
heat  of  vaporization  at  the  temperature  of  the  body.  The  amount 
of  heat  which  may  be  lost  by  evaporation  of  water  on  the  skin 
varies  within  very  wide  limits.  It  depends  on  the  amount  of  per- 
spiration secreted,  or  the  temperature  and  relative  humidity  of  the 
atmosphere  and  the  velocity  of  the  currents  of  air  to  which  the 
body  is  exposed.  When  saturation  of  the  atmosphere  exists  and 
the  external  temperature  is  less  than  that  of  the  body,  evaporation 
can  still  take  place  at  the  surface,  but  when  the  temperature  of  the 
surrounding  medium  is  equal  or  greater  than  that  of  the  body,  no 
evaporation  can  take  place,  and  consequently  no  heat  can  be  lost  to 
the  body  by  this  means. 

3d.  Heat  may  be  lost  by  the  warming  of  ingesta,  and  this  applies 
to  the  inspired  air.  This  is  only  possible  when  the  ingesta  are 
colder  than  the  body,  since  as  we  have  already  seen  in  the  reverse 
case  heat  will  be  gained.  It  is  stated  in  most  physiologies  that 
heat  is  lost  to  the  body  through  the  expulsion  of  the  urine  and 
faeces,  but  a  little  consideration  will  show  that  the  temperature 
cannot  be  affected  by  this  means,  while  if  the  substances  from  which 
these  products  are  derived  were  originally  ingested  warmer  than 
the  body  there  must  be  a  net  gain  of  heat.  Accordingly  the  urine 
and  faeces  have  no  place  in  our  problem. 

4th.  Heat  may  be  lost  to  the  body  by  the  expansion  of  air  in  the 
lungs  during  the  process  of  breathing.  Let  us  consider  carefully 
the  changes  taking  place  during  the  respiratory  cycle.  For  the 
average  individual  the  capacitv  of  the  chest  at  the  beginning  of  in- 


Thermii-s  and   Thermo-Dijnamics  of  the  Body.  9 

spiration,  including-  bronchial  nd  nasal  passages,  is  about  3,000  ccs. 
The  tidal  air  is  approximately  500  ccs.  This  is  the  amount  expired 
or  inspired,  and  the  two  quantities  are  sensibly  equal.  During 
each  breath  there  is  an  interchange  of  gases  between  the  blood  and 
the  air  in  the  lungs,  4  per  cent,  of  the  oxygen  of  the  inspired  air 
being  transferred  to  the  haemoglobin  of  the  blood,  while  the  par- 
tial pressure  due  to  the  oxygen  is  replaced  by  an  equal  volume  of 
carbonic  dioxide  from  the  blood.  Since  the  loss  of  pressure  from 
absorption  of  the  oxygen  is  at  each  instant  made  good  by  a  corres- 
ponding substitution  of  carbonic  dioxide,  we  may  consider  the 
dynamics  of  the  expansion  and  compression  of  the  gases  in  the 
lungs  without  regard  to  these  interchanges. 

We  may  liken  the  action  of  the  chest  to  the  stroke  of  a  piston  in 
a  cylinder.  Since  the  orifices  by  which  the  air  is  admitted  to  the 
lungs  is  relatively  small  to  their  capacity,  it  follows  that  if  the  ex- 
pansion takes  place  faster  than  the  air  can  rush  in  we  shall  have  at 
first  a  brief  period  in  which  the  pressure  of  the  air  in  the  lungs 
sinks  to  a  minimum,  when  the  inrushing  air,  which  increases  with 
the  difference  of  pressure,  externally  and  internally,  is  at  length 
suf^cient  to  prevent  the  pressure  sinking  any  lower.  This  mini- 
mum pressure  is  preserved  until  the  end  of  the  stroke  when  an 
equlibrium  is  again  established  between  the  external  and  internal 
pressures. 

During  the  return  stroke,  which  is  the  act  of  expiration,  the  pres- 
sure is  increased  in  the  limgs  to  a  maximum  until  the  rate  of  out- 
Avard  flow  prevents  a  further  rise.  This  maximum  is  maintained 
until  the  end  of  the  stroke,  when  by  expansion  the  external  and 
internal  pressures  are  once  more  brought  into  equilibrium.  Prac- 
tically, for  rapid  breathing,  we  may  consider  the  act  of  respiration 
as  simply  a  forward  and  backward  stroke  with  alternating  mini- 
mum and  maximum  pressures,  and  that  no  air  leaves  the  cylinder 
except  while  the  piston  is  in  motion. 

What  the  maximum  and  minimum  pressures  in  the  ultimate  air 
cells  are  we  do  not  know,  but  experiments  show  that  in  the  trachea 
these  pressures  are  about  70  mnis.  of  mercury  above  and  below  the 
atmospheric,  for  ordinary  breathing.  Since  the  lungs  (with  excep- 
tions) are  emptied  quicker  than  they  are  filled,  there  is  some  reason 
to  suppose  that  simultaneously  with  inspiration  the  bronchioles 
contract  and  with  expiration  relax.*     Their  structure,  the  folded 


'■  This  may  be  reversed  to  obtain  peculiar  effect-;  of  respiration,  as  we  shall  see  later  on. 


10  Therniics  and   T/irniio-ViiiHiiiiics  of  llic   Bodij. 


arrangement  of  the  mucous  membrane  and  the  circular  muscular 
fibres  surrounding  them  would  seem  to  support  this  view. 

It  is  a  n^atter  of  frequent  observation  that  a  warm-blooded  ani- 
mal maintains  its  proper  temperature  in  a  much  higher  atmosphere 
for  an  indefinite  time. 

It  is  usually  explained  that  this  equilibrium  is  maintained  b}'  the 
evaporation  of  the  perspiration  from  the  skin  with  perhaps  a  cer- 
tain amount  from  the  lungs.  It  is  true  that  a  large  amount  of  heat 
is,  under  ordinary  circumstances,  so  dissipated,  and  if  we  suppose 
the  air  to  be  perfectly  dry,  an  unlimited  amount  of  perspiration  to 
be  secreted  and  the  body  to  be  exposed  to  a  draught  of  very  high 
velocity,  there  is  scarcely  a  limit  which  can  be  put  to  the  tempera- 
ture which  the  body  coidd  not  theoretically  endure.  But  if  we 
suppose  the  atmosphere  to  be  saturated  (and  of  higher  tempera- 
ture), we  can  have  no  water  evaporated  from  the  skin.  But  we 
know  that  a  body,  even  under  these  conditions,  may  maintain  its 
temperature.  It  is  evident  that  the  thermotaxic  mechanism  can 
bring  about  such  a  result  by  two  means  acting  conjointly,  and  only 
by  two  means.  First  the  penetrability  of  the  l:»ody  is  diminished, 
and  with  it  the  quantity  of  heat  which  enters  the  body  from  with- 
out. But  this  is  not  sufficient.  Secondly,  there  nmst  be  an  ab- 
sorption of  heat  in  the  body.  We  shall  now  see  that  this  absorp- 
tion is  brought  about  b\-  a  peculiar  kind  of  respiration  whereby  a 
greater  weight  of  aqueous  vapor  is  expired  than  is  inspired  and 
by  the  expansion  of  air  in  the  lungs. 

It  will  be  observed  that  the  manner  of  breathing  differs  widely 
under  various  conditions  according  as  heat  is  to  be  absorbed,  or 
economized  to  the  utmost,  or  possibly  to  be  generated  in  the  lungs. 
In  a  Turkish  bath,  or  on  a  very  hot  day,  the  frequency  of  respira- 
tion is  much  increased,  l^esides  having  other  peculiarities.  This 
can  be  observed  in  a  shaggy-haired  dog  on  a  very  hot  day,  breath- 
ing one  hundred  or  more  times  a  minute,  the  expirations  taking 
place  with  explosive  suddenness.  The  animal  having  no  surface 
evaporation  is  obliged  to  run  his  lungs  as  a  cooling  machine  in 
order  to  maintain  his  temperature.  When  going  into  a  very  cold 
atmosphere  (if  naked)  the  frequency  of  respirations  is  much  re- 
duced. A  deep  inspiration  (gasp)  is  caught  and  the  whole  air  is 
held  compressed  in  the  lungs  for  a  long  time  before  it  is  explosively 
expelled  and  the  process  repeated.  Here,  as  we  shall  afterwards 
see,  heat  is  absorbed  to  a  minimum  degree  or,  when  the  external 


TliermiCH  and  Thermo-Dynamics  of  the  Body.  11 

and  internal  temperatures  have  not  too  great  a  difference,  heat  may 
actually  be  gained  by  the  compression  of  the  air. 

Dynamically  we  may  consider  the  residual  air  as  remaining  per- 
manently in  the  lungs  (though  this  is  not  actually  the  case),  the 
tidal  air  flowing  in  and  out  with  each  stroke.  The  air  in  the  body 
is  in  relation  peripherally  with  the  respiratory  mucous  membrane, 
and  centrally  it  is  in  the  closest  contact  with  the  pulmonary  plexus. 
Both  tracts  are  excellent  conductors,  but  the  capillaries  must  be 
much  the  better  of  the  two.  This  capillary  conductivity  may  be 
still  more  increased  by  an  increase  of  the  blood  stream  through 
the  lungs.  It  will  thus  be  seen  that  when  the  lungs  are  laboring 
to  absorb  heat,  for  the  cold  so  produced — if  we  may  use  this  re- 
verse phraseology — to  be  taken  up  and  distributed  at  a  maximum, 
a  certain  increased  flow  of  blood  is  necessitated,  and  this  the  ther- 
motaxic  mechanism  provides  by  an  increased  heart  action.  We 
see,  therefore,  that  when  the  economy  is  struggling  to  maintain  its 
temperature,  increased  respiratory  activity  always  takes  place  con- 
currently with  increased  heart  activity.  When  in  this  struggle  the 
economy  finally  succumbs,  we  have  seen  that  where  death  is  not 
due  directly  to  the  disturbance  caused  by  the  increasing  tempera- 
ture, it  arises  from  respiratory  or. heart  failure.  These  failures  are 
to  be  considered  not  alone  an  exhaustion  of  nerve  centres,  but  of 
muscular  tissues  as  well.     Perhaps  the  latter  is  the  larger  factor. 

In  the  following  discussion  I  shall  let  P  represent  the  pressure  of 
the  atmosphere,  T  the  temperature  of  the  body  and  3  the  tempera- 
ture of  the  atmosphere.  Let  p  be  the  minimum,  and  p,  the  maxi- 
mum pressure  of  the  air  in  the  lungs  during  any  respiration. 

I  shall  consider  first  the  aqueous  vapor  in  the  lungs  at  different 
stages  of  the  respiratory  cycle.  Let  the  relative  humidity  of  the 
atmosphere  be  r.  If  we  suppose  a  half  litre  of  this  air  to  be  in- 
spired at  each  breath,  which  is  an  average  amount,  it  will  contain: 

,  1.293  I  /&  r  1 

§  X X  ,  X—:?—  X  r=  (^  grammes  of  water,  where 

2  i  +  a(i — 273)     760  *^ 

/^  is  the   partial    pressure    of  saturated  aqueous  vapor  at  tem- 
perature S^  and  «-=  .00367. 

Let  us  now  suppose  that  by  the  return  stroke  the  pressure  is 
raised  to  p  .  If  this  return  stroke  be  executed  slowly,  the  air  in  the 
lungs  will  nearly  maintain  a  temperature  T  and  be  compressed  iso- 
thermally.  A  certain  amount  of  water  will  be  condensed,  but  if 
the  return  stroke  be  executed  suddenly  it  will  approach  towards 
a  limiting  condition  where  the  air  is  compressed  adiabatically  and 


12  Thermlcs  and   Tliernid-jMi  ninnies  of  I  lie  Bodij. 


the  tidal  air,  since  conduction  is  a  function  of  the  time,  will  be  ex- 
pelled before  it  has  time  to  part  with  its  heat  of  compression,  or 
with  any  of  its  aqueous  vapor.  It  is  to  be  remarked  that  the  air  in 
the  lungs  is  at  all  times  saturated. 

We  may  suppose  that  the  inspired  air  at  the  end  of  inspiration  will 
have  acquired  the  temperature  of  the  blood,  although  the  expired 
air  may  not  have  time  to  do  so  before  being  expelled,  for  the  fol- 
lowing reasons:  First,  as  the  inspired  air  swirls  in,  it  is  carried  by 
its  momentum  inwards  against  the  rapidly  flowing  blood  current, 
so  that  the  major  part  of  the  expired  air  is  the  original  air  in  the 
lungs.  Secondly,  coincidently  with  the  compression  of  expiration, 
the  expired  air  begins  to  leave  the  body,  so  that  at  any  subsequent 
instant  only  a  fraction  of  it  remains  inside  the  body.  Thirdly,  the 
time  of  inspiration  is  usually  longer  than  that  of  expiration. 

The  mass  of  the  expired  air,  if  oringinally  at  temperature  T  and 
compressed  adiabatically  from  pressure  p   to   pressure  p,  ,  will  be 

raised   to   the   temperature    ti=(-!-j     T,  where  y=  -  and    k  is 

the  ratio  of  the  specific  heat  of  air  at  constant  pressure  to  that  at 

constant  volume.     This  mass  of  air  must  take  up  sufificient  water 

to  saturate  itself  at  its  volume,  pressure  and  temperature. 

The  weight  of  water  necessary  to  saturate  this  mass  under  the 

1.293                     I  -/ti  Pt, 

conditions  is   :   4  X     X    — , — — r    X    ■:-—    x    — K=h 

2  I  -|-<7(t, — 273)         760         p,S 

grammes  wljere/ti  is  the  partial  pressure  of  saturated  aqueous 
vapor  at  temperature  ti.  If  b  >a,  there  must  be  an  evapora- 
tion  of   water  at  every  breath. 

We  have  considered  in  the  above  discussion  only  the  aqueous 
vapor  in  the  tidal  air  since,  the  residual  air  always  returning  to  ini- 
tial conditions,  the  sum  of  the  evaporations  and  condensations 
must  be  equal  for  the  complete  cycle. 

We  shall  next  consider  the  dynamic  changes  in  the  lungs  on  the 
supposition  that  the  air  is  dry.  If  we  suppose  the  mass  of  the  re- 
sidual air  to  be  M  and  that  of  the  tidal  air  to  be  m,  and  that  the  ex- 
pansion from  pi  to  p,  and  the  compression  from  p  to  p,  is  per- 
formed so  quickly  as  to  be  adiabatic.  and  that  at  end  of  inspiration 
and  expiration  the  temperatures  coincide  with  that  of  the  blood,  we 
may  write  the  quantity  of  heat  extracted  by  the  residual  air  from 
the  blood  during  expansion  MS|,(T — (i\)    T)  and  that  restored 

during   compression   Ms^((— j^T — T.)       These  quantities   will 


Therm>vt<  and   Thermo- Dynamic^;  of  the  Body.  13 

not  be  precisely  the  same,  since  more  work  is  clone  in  the  latter  case 
than  in  the  former. 

If  we  suppose  the  tidal  air  to  be  first  raised  to  the  temperature  of 
the  body  and  then  expanded  isothermally,  we  have  as  an  expres- 
sion for  the  heat  abstracted  from  or  added  to  the  blood,  according 
to  sign,  M  s^,  (T^ — S)  +  7  log  I,  where  V  is  the  volume  of  the 
tidal  air  at  T,  P,  and  J  is  the  mechanical  equivalent  of  heat.  Sp. 
is  the  specific  heat  of  air  at  constant  pressure.  During  the  reverse 
stroke  the  mass  m  of  the  tidal  air  is  compressed,  let  us  suppose, 
adiabatically  from  p  to  p,  .  Coincidently  with  the  compression, 
however,  it  begins  to  leave  the  body.  If  the  conduction  were  such 
that  this  mass  if  retained  inside  the  body  would  give  up  all  its  heat 
in  the  time  of  the  return  stroke,  it  can  be  shown  that  when  at  the 
end  of  the  stroke  no  tidal  air  is  left  in  the  body,  but  one-third  of 
this  heat  can  be  given  to  the  blood.  As  the  expulsion  of  this  tidal 
air  becomes  more  sudden,  a  limiting  condition  is  approached  in 
which  none  of  this  heat  is  given  up  to  the  blood. 

Under  the  conditions  specified  we  can,  therefore,  write  the  total 
heat    lost    or     gained     (according     to    sign)     by     the    blood, 

Ms..  T  (i_(^)r)_Ms„T  (Q)r-i)+m  s,,  (T-S)+7  log  ?  = 

Q  or  calling  p  =1,  we  have  2  M  s,.  T — Ms^  T  (1  ^'  -f- 1--*  )  +  m  s^, 
(T — S)  -^L' log  -  =  Q.  Assuming  for  a  particular  case  that 
li  =  -x\  and  'p=y't>  '^^'^  ^"'^  ^^''^^  2  Ms^,  T=44i.75  and  Ms^  T 
(K  +1 — '''')  =445.5,  while  '7  log  p  is  approximately  equal  to  4 
calories.      If  S=  T  we  have,  therefore,  Q=  445.75 — 445-5- 

We  thus  see  that  from  the  adiabatic  compression  and  expansion 
of  dry  air,  but  little  heat  c-an  be  absorbed  during  the  cycle. 

If  the  expansions  and  compressions  take  place  isothermally  no 
heat  can  be  gained  or  lost  from  the  residual  air.  For  ordinary 
conditions  we  have  seen  that  about  4  calories  is  absorbed  by  the 
expansion  of  the  tidal  air. 

Let  us  now  consider  how  heat  may  be  lost  or  gained  by  pecu- 
liarities of  breathing.  Taking,  first,  strictly  norinal  conditions, 
we  will  suppose  that  the  atmosphere  is  somewhat  below  the  tem- 
perature of  the  body  and  below  the  saturation  point.  Respiration, 
under  these  conditions  taking  place  slowly  and  gently,  the  maxi- 
mum and  minimum  pressures  do  not  deviate  greatly  from  that  of 
the  atmosphere.     Expiration  takes  place  so  slowly  that  we  may 


14  Tlwrmics  and   Thn-mo-Di/namics  of  the  Bo(hj. 

suppose  a  considerable  portion  of  the  heat  of  compression  to  be 
given  up  to  the  circulation  before  the  tidal  air  leaves  the  body. 
Practically  no  heat  will  be  gained  or  lost  from  the  tidal  air.  The 
aqueous  vapor  of  the  tidal  air  enters  the  body  at  the  pressure  and 
temperature  of  the  atmosphere,  leaving  it  at  the  temperature  of  the 
body  and  pressure  pi.  A  certain  amount  of  water  will  therefore  be 
evaporated  in  the  lungs.  The  evaporation  of  this  water  and  the 
warming  of  the  tidal  air  will,  therefore,  absorb  a  moderate  amount 
of  heat  which  will  play  an  important  role  in  maintaining  the  equi- 
librium of  the  body. 

Let  us  next  consider  the  body  placed  (naked)  in  a  very  cold  at- 
mosphere. There  will  at  first  be  a  very  rapid  loss  of  heat  at  the 
surface,  with  the  thermotaxic  mechanism  quickly  checks  by 
shutting  ofif  the  peripheral  circulation.  But  it  is  important  that 
the  moderate  absorption  of  heat,  which,  we  have  seen  above,  takes 
place  during  ordinary  breathing,  should  be  reduced  to  a  minimum. 
This  can  be  done  by  compressing  strongly  the  tidal  air  in  the  lungs 
by  means  of  the  chest  muscles  and  holding  it  so  compressed  for 
quite  a  long  period,  after  which  it  is  suddenly  expelled  and  the  pro- 
cess repeated.  By  holding  it  compressed  it  will  have  time  to  give 
up  all  its  heat  of  compression  to  the  circulation,  and  besides  the 
aqueous  vapor  in  it  will  be  reduced  to  a  minimum,  viz.,  the  amount 
necessary  to  saturate  its  small  mass  at  the  temperature  of  the  body 
and  the  high  pressure  pi- 

By  such  a  means  of  breathing  the  heat  usually  absorbed  by  the 
lungs  is  reduced  to  a  minimum  and,  if  the  difiference  of  tempera- 
ture of  the  body  and  atmosphere  are  not  too  great,  there  may  be 
even  a  generation  of  heat  in  the  lungs. 

As  a  matter  of  fact,  after  a  plunge  into  cold  water,  or  between 
the  sheets  of  a  cold  bed,  precisely  such  a  peculiar  kind  of  respira- 
tion is  observed  as  could  have  no  other  effect  than  that  mentioned 
above.  The  breathing  consists  of  a  deep  gasp  which  draws  in  the 
greatest  amount  of  air  possible  and  then,  all  means  of  exit  being 
closed,  it  is  firmly  compressed  and  held  so  for  a  long  interval,  at  the 
end  of  which  the  tidal  air  is  explosively  expelled  and  the  process 
repeated.  It  is  evident  that  from  the  exaggerated  compression  a 
high  initial  temperature  is  acquired  and,  from  the  prolonged  con- 
tact with  the  pulmonary  capallaries  ample  time  is  given  the  air  to 
part  with  all  its  heat  above  the  temperature  of  the  blood,  and  to 
condense  the  greatest  amount  of  moisture  possible,  by  means  of  the 
high  pressure.     The  tidal    air   is    then,    under   these    conditions, 


Thermk:<:  and   Theimu- Dynamics  of  the  Body.  15 


launched  out  of  the  body  suddenly,  no  time  being  given  for  it  to 
take  up  any  heat  either  by  evaporation  or  expansion. 

Let  us  suppose  now  that  the  body  be  placed  in  a  saturated  atmos- 
phere or  water  of  a  higher  temperature  than  the  body.  Here  no 
heat  can  be  lost  by  evaporation  by  the  skin,  on  the  contrary  heat  is 
passing  continually  into  the  skin.  The  gain  of  heat  is  everywhere 
positive  except  in  the  lungs,  and  there  heat  enough  must  be  ab- 
sorbed to  maintain  the  equilibrium.  How  shall  the  lungs  work 
so  as  to  effect  this  increased  absorption  of  heat?  First  a  deep  in- 
spiration so  as  to  get  a  large  amount  of  tidal  air,  but  the  most  im- 
portant part  is  the  expiration.  A  sudden  compression  develops  an 
instantaneous  increase  of  temperature  and  with  it  an  evaporation 
of  water  sufficient  to  saturate  the  air  at  the  temperature  and  pres- 
sure. These  two  factors — temperature  and  pressure — to  be  sure, 
work  in  opposite  directions,  but  the  temperature  is  much  the  more 
important  of  the  two.  A  large  amount  of  water  is  momentarily 
evaporated,  and  this  must  be  suddenly  expelled,  otherwise  the  air 
will  have  time  to  cool  down  and  give  back  heat,  first  by  condensa- 
tion, second  by  conduction. 

The  writer  has  observed,  under  the  conditions  given,  precisely 
this  kind  of  respiration.  Where  a  maximum  efifect  is'  necessary, 
the  respirations,  each  of  this  peculiar  kind,  are  much  increased  in 
frequency.  The  case  of  the  shaggy-haired  dog  has  already  been 
noted.  The  action  of  the  heart  is  coincidently  much  increased  in 
order  to  distribute  rapidly  the  cold  so  gained  by  the  lungs. 

Recurring  to  our  expressions  for  a  and  b  above,  we  see  that 
there  must  be  a  certain  critical  temperature  for  every  warm- 
blooded animal  beyond  \\  hich  it  cannot  maintain  its  existence  in  a 
saturated  atmosphere.     ,^ 

That  is  to  say,  theoretically,  at  this  point  it  will  be  able  to  keep 
its  temperature  normal,  while  for  a  slight  excess  there  will  be  a 
steady  accumulation  of  heat  in  the  body,  which  will  result  in  death 
by  heat.  Such  death  we  know  clinically  takes  place  under 
three  chief  forms  which  may  be  merged  into  each  other.  First, 
death  may  be  due  to  simple  elevation  of  temperature.  We  know 
that  the  vital-chemical  processes  of  the  body  can  only  take  place 
within  a  very  narrow  range  of  temperatures,  just  as  in  the  labora- 
tory certain  reactions  require  a  definite  temperature.  When  this 
temperature  is  increased  the  vital-chemical  reactions  in  all  the  tis- 
sues are  disturbed.  The  normal  action  of  the  brain  cells  is  changed 
— coma  results.     The  muscles  also  change  their  composition  and 


16  Tlwrinlrs.  and   TltiTino-DijiKimic,^  of  the  Body. 


their  function  of  transforming-  the  potential  energy  of  various 
compounds  into  kinetic  energy  becomes  deranged.  Such  >a.  form 
of  death  takes  plac<=^  if  the  '"ngs  i^nd  heart  have  been  able  to  hold 
out  thus  long  in  the  unequal  contest.  When  one  or  the  other  suc- 
cumbs to  the  excessive  strain  put  upon  it,  we  have  death  by  res- 
piratory or  heart  failure,  which  are  familiar  enough  forms  to  prac- 
titioners who  have  seen  many  cases  ot  sun  stroke. 

Let  us  suppose  that  we  have  a  saturated  atmosphere  of  80°,  and 
that  the  ratio  l=i^i,  perhaps  an  average  value.  Under  these  con- 
ditions we  find  that  a=.i45  and  b=.i32  a  >  b.  Consequently 
heat  will  be  gained  with  every  1)reath  and  the  individual  could 
not  long  survive.  80°  therefore  is  above  the  critical  temperature 
for  a  human  being  where  the  tidal  air  is  about  half  a  litre  and  the 
ratio  1  cannot  much  exceed  A- 

If  A  is  the  quantity  of  heat  that  enters  or  leaves  the  surface  of 
the  body  (according  to  sign),  B  is  the  heat  generated  by  the  heart, 
and  C  is  the  heat  due  to  katabolism.  all  in  the  time  of  one  respira- 
tion, we  may  write  A  -|-  B  -f-  C  -f-  m  s,,  (^ — T)  =  (b — a)  L,,  * 
where  L  r  is  the  latent  heat  of  water  at  temperature  T.  All 
these  quantities  except  C  are  capable  of  direct  measurement,  and 
knowing  the  others,  C  can  be  found.  When  the  body  is  at  rest  it  is 
probable  that  this  value  is  very  small.  For  high  temperatures 
also,  certain  experiments  of  the  writer  indicate  that  A  is  quite  small. 
We  may  give  then  as  an  approximate  value  of  the  critical  tempera- 
ture of  the  human  being  65''  or  yo°  (about  155°  Fahr.). 

It  would  be  eminently  desirable  if  observations  upon  a  warm- 
blooded animal  could  be  carried  out  from  a  strictlv  thermo-dy- 
namical  point  of  view.  Such  experiments,  requiring  the  conven- 
iences of  a  laboratory,  the  writer  has  not  had  the  opportunity  of 
carrying  out. 


*  A  small  term — the  heat  necessary  to  raise  (b-a)  grammes  of  vaijonr  from  T  to  t; — is  here 


neglected 


COLUMBIA   UNIVERSITY 

This  book  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing, 
as  provided  by  the  rules  of  the  Library  or  by  special  ar- 
rangement with  the  Librarian  in  charge. 

DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

C2Sf638)MS0 

QP135 


C81 


Cordeiro 

Thermic s  and  the rmo -dynamics  of 


f 


